1. Field of the Invention
The present invention relates to a portable wireless apparatus and an antenna device, suitable for a portable telephone in which the use in, for example, an automobile has been taken into consideration.
2. Description of Related Art
In recent years, portable telephones have become noticeably popular, but further miniaturization and weight reduction are being advanced in order to improve the portability, and antennas are also requested to be small-sized accordingly.
Conventionally, as an antenna for a portable telephone, there has been frequently used a disappearing whip antenna which is housed in the main body during carrying, and is drawn out from the main body during a call. This antenna is prevented from being damaged during carrying, and is convenient for carrying, while during a call, the influence of cut-off radio waves due to the human head is reduced by making the antenna length (height) large to improve the call quality.
On the other hand, in the case of using a portable telephone in an automobile, since sufficient sensitivity cannot be obtained only by a built-in antenna of the portable telephone surrounded by the metallic body, it is arranged such that sufficient sensitivity can be obtained even in the automobile by separately installing another antenna on the automotive window or on the outside of the body to connect the portable telephone to this external antenna. In this respect, when connected to the external antenna, the built-in antenna of the portable telephone is disconnected.
Such a portable telephone in which the use in an automobile has been taken into consideration as described above has been conventionally constructed as shown in, for example, FIG. 7 or FIG. 8.
In a portable telephone 10 shown in FIG. 7, a connector 12 for an external antenna is arranged facing an opening 11b at the bottom end portion of a housing 11 made of synthetic resin, and a circuit substrate 13 is housed inside the housing 11.
The connector 12 comprises a jack 12j in which a plug (not shown) connected to a feeding cable (not shown) for the external antenna is inserted, and a normally-closed switch 12s mechanically coupled to the jack 12j. In this respect, this connector 12 explains structure of the principle, and the present invention is not limited to such a connector type.
A RF transmitter-receiver circuit 14 packaged in the circuit substrate 13 is connected to the jack 12j, and is also connected to a feeding spring 17 arranged at the top end portion of the circuit substrate 13 through the normally-closed switch 12s, a feeding path 15 and a matching circuit 16.
On the upper surface of the housing 11, an opening is formed inside a convex ridge 11a, and a supporting fitting (holder) 22 for a rod antenna 21 is fitted in the opening so that the tip end portion of the feeding spring 17 elastically comes into contact with the outer surface of the holder 22. The rod antenna 21 is formed by a linear conductor, and its base is slidably supported by the holder 22 formed in a cylindrical shape.
In this respect, the length of the rod antenna 21 is set so that a portion above a contact point with the feeding spring 17 in a state in which the rod antenna 21 has been drawn out as shown in FIG. 7 is .lambda./4 (.lambda. is a wave length of the radio communication frequency band in length.
In such a portable telephone 10 in FIG. 7 as described above, when the plug for an external antenna is inserted into the jack 12j in the connector, the normally-closed switch 12s is opened to disconnect the rod antenna 21, and also the RF transmitter-receiver circuit 14 is connected to only the external antenna (not shown).
On the other hand, in a portable telephone 10C shown in FIG. 8, a connector 12C for an external antenna is arranged facing an opening 11b at the bottom end portion of a housing 11 made of synthetic resin, and a circuit substrate 13 is housed inside the housing 11.
The connector 12C comprises a jack 12j in which such a plug (not shown) for the external antenna as described above is inserted, and a sensor (not shown) for detecting the insertion of the plug into this jack 12j, and an output signal from this sensor is supplied to a control circuit 18 through a terminal 12d.
A RF transmitter-receiver circuit 14 packaged in the circuit substrate 13 is connected to the traveling contact of a change-over switch 19. This switch 19 is constituted by, for example, a field-effect transistor, and is change-over controlled through a control signal from the control circuit 18. A o-side fixed contact of the switch 19 is connected to the jack 12j, and an i-side fixed contact of the switch 19 is connected to a feeding spring 17 arranged at the top end portion of the circuit substrate 13 through the matching circuit 16.
On the upper surface of the housing 11, an opening is formed inside a convex ridge 11a, and a supporting fitting (holder) 22 for a rod antenna 21 is fitted in the opening so that the tip end portion of the feeding spring 17 elastically comes into contact with the outer surface of the holder 22. The rod antenna 21 is formed by a linear conductor, and its base is slidably supported by a holder 22 formed in a cylindrical shape.
In this respect, the length of the rod antenna 21 is set so that the portion above the contact point with the feeding spring 17 is .lambda./4 in length in a state in which the rod antenna 21 has been drawn out as shown in FIG. 8.
In such a portable telephone 10C in FIG. 8 as described above, when the plug for an external antenna is not inserted into the jack 12j in the connector 12C, the traveling contact of the change-over switch 19 is connected to the i-contact side as shown in FIG. 8 so that the RF transmitter-receiver circuit 14 is connected to only the rod antenna 21.
When the plug is inserted into the jack 12j, the traveling contact of the change-over switch 19 is changed over to the o-side of the change-over switch 19 contrary to the illustration so that the rod antenna 21 is disconnected and the RF transmitter-receiver circuit 14 is connected to only the external antenna (not shown).
In such a conventional portable telephone 10, 10C in which the use in an automobile has been taken into consideration as described above, the rod antenna 21 is arranged at the top end portion of the housing 11 in order to avoid the influence due to the human body during a call, and the feeding spring 17 is also provided at the top end portion of the circuit substrate 13 accordingly.
Also, the connector 12, 12C for the external antenna is provided at the bottom end portion of the housing 11 in order to reduce the cumbersomeness of the feeding cable during the use in an automobile.
In such a portable telephone 10 as shown in FIG. 7, however, since the RF transmitter-receiver circuit 14 arranged near the connector 12 is apart from the matching circuit 16 and the feeding spring 17, the feeding path 15, through which a RF signal is transmitted when the built-in antenna 21 is in use, becomes long so that the transmission loss due to this path 15 reaches, for example, about 1 dB.
In order to cover the transmission loss due to the feeding path 15, severe specifications are requested for the antenna system and the RF system circuit, and this has led to a problem that the manufacturing cost will be increased.
On the other hand, in such a portable telephone 10C as shown in FIG. 8, the feeding path when the built-in antenna 21 is in use can be shortened by the provision of an electronic change-over switch 19 in the vicinity of the RF transmitter-receiver circuit 14, but it has a problem that the manufacturing cost will be increased by the adoption of a connector 12C with a sensor and the change-over switch 19.
In light of the above-described points, an object of the present invention is to provide a portable wireless apparatus and an antenna device which have reduced the transmission loss between the RF transmitter-receiver circuit arranged in the vicinity of the external antenna connector and the built-in antenna.